Real time straightness deviation measuring and compensation device for machine tools

Abstract

A real time straightness deviation measuring and compensation device for a machine tool that automatically and continuously compensates for bed way deviation from a truly straight line relative to a workpiece. A wire, parallel to the workpiece or axis of workpiece rotation and perpendicular to the direction of machine tool compensation is utilized as a straightness reference, with the wire being stretched in the direction of machine tool carriage travel and supported on either end by weights for gravity induced straightness. A position indication device, such as a laser micrometer, is attached to the machine tool carriage and positioned around the reference wire in order to read the position of the wire relative to the machine tool carriage during real time operation. An electronically controlled servo motor attached to a machine tool supported on the carriage automatically adjusts the machine tool to compensate for carriage deviation caused by bed way deviation relative to the straight reference wire.

What is claimed is: 
     
       1. A real time straightness deviation measuring and compensation device for a machine tool acting on a workpiece, the measuring and compensation device comprising: a bed having a bedway;   a carriage supported by said bedway for rectilinear movement thereon, said carriage having said machine tool movably supported on an upper surface thereof;   a reference line aligned parallel to an axis of desired rectilinear carriage movement, said reference line being independent of said bedway and fixed relative to said bed;   means for determining deviation of movement of said carriage in a direction transverse to said reference line during said rectilinear movement; and   compensation means responsive to said determining means for controllably moving said machine tool relative to said carriage in response to measured deviation of movement of said carriage from said reference line.   
     
     
       2. The device of claim 1, wherein said compensation means controllably moves said machine tool in a direction transverse to said rectilinear movement of said carriage. 
     
     
       3. The device of claim 1, wherein said determining means is a laser micrometer. 
     
     
       4. The device of claim 1, wherein said determining means is disposed on said carriage. 
     
     
       5. The device of claim 1, wherein said reference line is a wire. 
     
     
       6. The device of claim 5, further including tensioning means for inducing straightness in said wire. 
     
     
       7. The device of claim 6, wherein said wire has ends extending beyond said bed, and said tensioning means includes a weight attached to each said extending end for creating a gravity induced tension. 
     
     
       8. The device of claim 1, wherein said machine tool is a roll grinder. 
     
     
       9. The device of claim 1, wherein said determining means is operable to generate a signal indicative of the amount of orthogonal deviation of said carriage relative to said reference line. 
     
     
       10. The device of claim 9, wherein said compensation means comprises: servo means attached to said machine tool for moving said machine tool in a direction transverse to said rectilinear movement, said servo means including means for producing a servo velocity signal;   first means for comparing said carriage position signal with a predetermined part profile position signal, and producing a straightness corrected position signal thereby;   means for indicating the position of said machine tool relative to said carriage and generating a tool position indication signal;   second means for comparing said straightness corrected position signal with said tool position indication signal, and producing a position error velocity signal thereby; and   third means for comparing said position error velocity signal with said servo velocity signal, and generating a drive signal thereby;   said servo means responsive to said drive signal whereby said machine tool is moved by said servo means in response thereto.   
     
     
       11. The device of claim 10, wherein said servo means comprises: a motor;   gear means operably connected to said motor and said machine tool for translating rotational motor movement into transverse machine tool movement; and   an armature connected to said motor for receiving said drive signal and controlling said motor.   
     
     
       12. A real time straightness deviation measuring and compensation device for a machine tool acting on a workpiece, the measuring and compensation device comprising: a bed having a bedway;   a carriage supported by said bedway for rectilinear movement thereon, said carriage having said machine tool supported for orthogonal movement relative said rectilinear movement on an upper surface thereof;   a reference line aligned parallel to an axis of desired rectilinear carriage movement, said reference line being independent of said bedway and fixed relative to said bed;   means disposed on said carriage for determining deviation of movement of said carriage in a plane horizontally orthogonal to said reference line during said rectilinear movement; and   compensation means coupled to said determining means for controllably moving said machine tool relative to said carriage in a plane horizontally orthogonal to said rectilinear movement in response to deviation of movement of said carriage from said reference line as measured by said determining means.   
     
     
       13. The device of claim 12, wherein said determining means is a laser micrometer. 
     
     
       14. The device of claim 12, wherein said reference line is a wire. 
     
     
       15. The device of claim 14, further including tensioning means for inducing straightness in said wire. 
     
     
       16. The device of claim 15, wherein said wire has ends extending beyond said bed, and said tensioning means includes a weight attached to each said extending end for creating gravity induced tension. 
     
     
       17. The device of claim 12, wherein said machine tool is a roll grinder. 
     
     
       18. The device of claim 12, wherein said determining means is operable to generate a signal indicative of the amount of orthogonal deviation of said carriage relative to said reference line. 
     
     
       19. The device of claim 18, wherein said compensation means comprises: servo means attached to said machine tool for moving said machine tool in a direction transverse to said rectilinear movement, said servo means including means for producing a servo velocity signal;   first means for comparing said carriage position signal with a predetermined part profile position signal, and producing a straightness corrected position signal thereby;   means for indicating the position of said machine tool relative to said carriage and generating a tool position indication signal;   second means for comparing said straightness corrected position signal with said tool position indication signal, and producing a position error velocity signal thereby; and   third means for comparing said position error velocity signal with said servo velocity signal, and generating a drive signal thereby;   said servo means responsive to said drive signal whereby said machine tool is moved by said servo means in response thereto.   
     
     
       20. The device of claim 19, wherein said servo means comprises: a motor;   gear means operably connected to said motor and said machine tool for translating rotational motor movement into transverse machine tool movement; and   an armature connected to said motor for receiving said drive signal and controlling said motor.